Optimism 'reduces stroke risk'

“Being an optimist can cut your risk of stroke,” the Daily Mail has reported today. The newspaper says that looking on the bright side of things can have a direct positive effect on physical health.

The news is based on a large US study which had assessed various aspects of health, lifestyle and outlook in more than 6,000 elderly participants. Researchers then followed them for a two-year period to see how optimism related to their chances of experiencing their first stroke. They performed various calculations to adjust for some of the numerous health and lifestyle factors that could potentially influence the relationship. During the follow-up period, 88 strokes occurred, and the researchers found that a higher optimism score was associated with lower risk of stroke.

However, some caution should be applied when considering these results, particularly as the follow-up period was short: those who went on to develop stroke were likely to have had cardiovascular disease developing at or before the time their optimism was assessed. This means we cannot assume that a person’s outlook caused their disease.

Nevertheless, this large study’s findings are consistent with previous research and commonly held theory that a positive outlook can have beneficial effects on health and wellbeing.

Where did the story come from?

The study was carried out by US researchers from the University of Michigan and was funded by the Robert Wood Johnson Foundation’s Pioneer Portfolio, a research fund that supports innovations in healthcare. The study was published in the peer-reviewed medical journal, Stroke.

News reports have generally reflected the findings of this research paper.

What kind of research was this?

This was a prospective cohort study which aimed to examine whether higher levels of optimism could be linked to a lower risk of stroke. Optimism has often been linked to positive health outcomes, particularly in cardiovascular disease (for example, in studies assessing people’s attitude after heart attack or heart surgery), but the researchers say that no study has investigated this theory regarding stroke, particularly in the elderly.

What did the research involve?

This research involved participants of The Health and Retirement Study, which is an ongoing, nationally representative study in the US that began in 1992. It has surveyed more than 22,000 Americans aged 50 and over every two years. This current study used psychological and health data collected in 2006 to investigate whether there was an association with the stroke outcomes collected in 2008.

In 2006, half of the study participants received an in-depth assessment with a face-to-face interview. The researchers excluded those who did not complete a psychological questionnaire, those who reported a history of stroke and those with incomplete data. This gave the researchers a final sample of 6,044 participants for inclusion in their study.

Optimism and pessimism were assessed separately, using a modified version of a test called the 6-item Life Orientation Test. The test assessed three items on each disposition, and participants were asked to use a six-point scale to rate their agreement with statements such as “In uncertain times, I usually expect the best”. The total score on the optimism score was from 3-18, with higher scores indicating greater optimism.

The researchers assessed a number of potential confounders that could have an association between both stroke and optimism:

chronic illness - e.g. cancer, lung disease, mental health problems

self-rated health - rated using a standard questionnaire called the Short Form 36

Stroke was defined as a first stroke recorded in 2008 – either by a self-reported doctor’s diagnosis if the participant was still alive, or by proxy report from another respondent if the stroke had been fatal. People who had experienced a transient ischaemic attack (TIA) were not classed as having had a stroke. TIAs, often called ‘mini-strokes’, are when the blood supply to the brain is briefly disrupted but symptoms resolve completely within 24 hours. They are usually due to a clot that temporarily blocks a blood vessel but then breaks up. While they do not cause lasting symptoms, they are a warning sign that the person is at risk of having a serious ischaemic stroke.

The researchers examined the relationship between optimism score in 2006 and stroke by 2008 using various models that took into account the numerous potential confounders that they identified.

What were the basic results?

The average age of people assessed was 68.5. Just over half were women. The average optimism score was reported to be 13.57 out of a maximum 18.

During the two-year follow-up, 88 strokes had occurred among the 6,044 participants. Each one-point increase in optimism score (possible range of 3-18) was associated with around a 10% decrease in the odds of experiencing a stroke according to the researchers’ core analysis model. This was a model that adjusted for age, gender, chronic illness and self-reported health (odds ratio [OR] 0.91, 95% confidence interval [CI] 0.85 to 0.98).

When the researchers produced a number of more-extensive models that made full adjustment for potential confounders, it did not affect the significance of the relationship presented by the core model. The researchers had initially looked at four of these extended models. While the first core model only adjusted for age, gender, chronic illness and self-reported health, each subsequent model added adjustments to incorporate data on social and demographic factors, health-related behaviour, biological measures or cardiovascular risk factors.

In particular, the researchers were interested to see whether the association between stroke and optimism was due to an ‘absence of negative psychological factors’, i.e. that the observed reduced risk seen in optimistic people, rather than being due to optimism as a trait in its own right, might reflect a lack of negative psychological traits. To assess, this they conducted a secondary analysis looking at the correlations between optimism and each of the negative psychological factors assessed (e.g. anxiety, negative mood). As expected, they found a negative correlation between them (i.e, the higher the optimism score the lower the negative psychological measure).

The researchers then tested whether these individual negative psychological factors were themselves independently associated with risk of stroke, and found that the odds of stroke were significantly increased if people displayed anxiety, depression, low mood and neuroticism, but not so with cynical hostility and pessimism.

In a sixth and final model they added these negative psychological factors one at a time to a model that featured adjustments for all potential confounders. Again, they found that the relationship between optimism and stroke remained significant. This suggests that optimism is protective against stroke and that the relationship is not simply due to the absence of negative psychological factors.

How did the researchers interpret the results?

The researchers conclude that “optimism may play an important role in protecting against stroke among older adults”.

Conclusion

This cohort study aimed to examine whether optimism could have any effect on the risk of stroke, and it examined the relationship in various models adjusting for different health, lifestyle and psychological factors. Optimism did appear to reduce the risk of stroke, but there are a few considerations to make:

Though the sample was large, only 88 strokes occurred during follow-up, which is a fairly small sample when looking at how the optimism scores of these people compared to those who did not have a stroke.

The assessment and follow-up are quite close in time, being only two years apart. Though the participants had no history of stroke at assessment, it is quite possible that the people who went on to develop stroke already had cardiovascular disease at the time the optimism assessment was made. In which case it would not be possible to say that their disposition had caused them to have a stroke if the disease process was already in place.

The stroke group did not include any people who had experienced a transient ischaemic attack (TIA). While these excluded people have not yet experienced a full stroke, if a person has had a TIA it suggests that they are at high risk of experiencing a stroke and that cardiovascular disease is present. It is arguable that these people are worthy of inclusion in either their own group or as part of the stroke group given the fact that patients experiencing a TIA are likely to progress to having a full stroke in future.

All health measures were assessed by self-report, which carries some risk of inaccuracy. However, the researchers say that self-reported health measures used in the Health and Retirement Study (HRS) have been rigorously assessed and have demonstrated substantial agreement with medical records. They also say that the validity of self-reported stroke as an accurate estimate of stroke incidence has been well-documented.

In particular, the researchers were concerned that an association between optimism and stroke would be simply due to the absence of negative psychological factors. They therefore analysed anxiety, cynical hostility, depression, negative effect, neuroticism and pessimism as separate confounders. They found that they did not affect the significance of the relationship. However, it is not possible to say from the published journal article how the presence of these factors in the individual had been measured. The paper says that details of these measures are available in the HRS Psychological Manual. This would be useful information to know in order to better see, for example, how examining an association between stroke and optimism score, while adjusting for pessimism, could have been conducted.

Nevertheless, this study’s findings are consistent with previous research and the commonly held theory that a positive outlook can have beneficial effects on health and wellbeing.